Grate element for a grate of a waste combustion installation

ABSTRACT

The present invention relates to a grate element ( 1 ) for a grate of a waste-incineration plant, having a plurality of rows of grate blocks, which are moveable or fixed, arranged one behind the other, a plurality of grate blocks ( 67 ) being arranged in each row of grate blocks. A first number of grate blocks arranged in a moveable row of grate blocks here is assigned to a first grate carriage ( 5 ), and a second number of grate blocks arranged in a moveable row of grate blocks is assigned to a second grate carriage ( 35 ), it being possible for the first number of grate blocks to be moved independently of the second number of grate blocks.

The invention relates to a grate element for a grate of awaste-incineration plant, having a plurality of rows of grate blocksarranged one behind the other.

Conventional inclined forward-feed grates for waste-incineration plantshave grate elements having a plurality of rows of grate blocks arrangedone behind the other, a moveable row of grate blocks being followed by afixed row of grate blocks. The moveable rows of grate blocks areassigned to a grate carriage, by means of which they are moved forwardand back (CH 585 372). The intermixing and the raking of the waste heretake place in the transporting direction.

The prior art also discloses a backward-feed grate, which is describedin a large number of patents, for example in DE 525221 and DE 1099117.Such a backward-feed grate is an inclined grate having alternately fixedand moveable rows of grate blocks. By virtue of the grate blocks of themoveable rows of grate blocks, the bottom layers of the waste which isto be incinerated are pushed in the direction of the start of the grate,the top layers moving in the direction of the end of the grate. Thewaste is thus pushed away counter to the transporting direction, withthe result that the waste is piled up at the start of the grate andconveyed downward by the gravitational force, this taking place, inpart, by way of an uncontrolled slipping action.

A further grate system which is well-known to the person skilled in theart is constituted by the W+E combustion grates, which are described,for example, in M. Kütnzli, Rostfeuerungen zur Abfallverbrennung [gratefurnaces for waste incineration], Dieter O. Reimann (Ed.), Berlin:EF-Verlag für Energie und Umwelttechnik, 1991, pages 1-17. Oppositelydirected movement of moveable rows of grate blocks here, which arearranged alternately with fixed rows of grate blocks, results not justin the waste which is to be incinerated being pushed forward, but alsoin it being continuously raked and circulated.

EP 1 001 218 describes a water-cooled combustion grate which comprises acombination of a forward-feed grate and of a backward-feed grate, bothhaving water-cooled grate plates, of which at least every second one isof moveable configuration.

U.S. Pat. No. 4,170,183 and FR 2 265 041 describe so-called longitudinalgrates of a waste-incineration plant. A longitudinal grate is understoodas being a grate which, in the transverse direction, i.e. transverselyto the transporting direction, has a plurality of moveable and fixedlongitudinal tracks extending over the entire length of the grate. Alongitudinal track here has a plurality of grate blocks arranged onebehind the other. Each fixed longitudinal track is followed by amoveable longitudinal track. The longitudinal grates described have aplurality of bars which allow the movement of the longitudinal tracks inthe transporting direction. The longitudinal grate is purely a conveyingsubassembly and allows only uncontrolled transportation of the waste.Since the movement of the longitudinal tracks takes place over theentire length of the grate, the transporting speed and thus theoperating conditions cannot be regulated independently in eachincineration zone.

A stepped grate is made up, in the transporting direction, of aplurality of grate elements, usually three to six grate elements beingarranged one behind the other. A stepped grate may comprise one to fivegrate tracks.

Each grate element has a plurality of rows of grate blocks arranged onebehind the other in a step-like manner in the transporting direction,the rows of grate blocks being fixed or moveable. That is to say, in thecase of the stepped grate with fixed and moveable rows of grate blocks,in contrast to the longitudinal grate, it is the rows of grate blocks,and not longitudinal tracks, which are moveable in each case. A row ofgrate blocks is formed in each case by a plurality of, for example 16 to30, grate blocks. The grate blocks may be water- or air-cooled. Thegrate blocks are fitted one beside the other on a block-holding tube andbraced together by means of a tie rod. Each grate block has a foot whichrests on the surface of the following grate block, as seen in thetransporting direction. In the case of a forward movement, the foot ofthe upper grate block thus passes over the surface of the grate blocktherebeneath in the transporting direction.

The object of the present invention is to provide a grate element in thecase of which the waste is mixed intensively and continuously andconveying takes place in a controlled manner.

The object is achieved by the grate element having the features ofpatent claim 1. Further advantageous embodiments are claimed in thedependent claims and outlined in the description.

According to the invention, a first number of grate blocks of a moveablerow of grate blocks is assigned to a first grate carriage and a secondnumber of grate blocks is assigned to a second grate carriage, the grateelement according to the invention being equipped with two gratecarriages. Dividing the grate blocks of a row or grate blocks betweentwo different grate carriages causes the movement capability of thefirst number of grate blocks to be independent of the movementcapability of the second number of grate blocks. This results in some ofthe grate blocks moving rearward, while the rest of the grate blocksmove forward. The independent movement capability of the grate blocksgives rise to additional lateral intermixing. Peaks and troughs of wasteare thus produced on the grate and are moved forward and back in analternating manner. This results in the waste being mixed and raked bothlaterally and in the transporting direction. By virtue of the extremelygood intermixing and conveying of the waste, the incineration sequencecan be better controlled since fewer deflagrations occur. Moreover, byvirtue of the continuous circulation, the waste only remains lying inthe same location for a short period of time, which results in the grateblocks being subjected to less thermal stressing. The grate elementaccording to the invention is thus less susceptible to malfunctioning,has a long service life and guarantees cost-effective operation.

Since the first number of grate blocks can be moved independently of thesecond number of grate blocks, different types of operation arepossible. It is thus possible to adjust the movement pattern of thegrate element in different ways depending on the type of waste. Dividingthe individual grate blocks widthwise in relation to the correspondinggrate carriages advantageously takes place in groups of five or sevengrate blocks. It would also be conceivable, however, for division totake place with a larger or smaller number of blocks or an even numberof blocks.

The surface area of the waste which is to be incinerated is increased bythe optimum circulation. The incineration process thus takes place morequickly and completely.

The grate element according to the invention is thus cost-effective andvery advantageous from an ecological standpoint.

The first grate carriage and the second grate carriage advantageouslyhave a guide arrangement with interacting guide elements. The guideelements ensure that the two grate carriages move on the tracksenvisaged for them and do not move apart from one another in space. Suchguide elements may be, for example, guide grooves and guide noses,although other guide elements known to the person skilled in the art arealso conceivable.

In a preferred embodiment, the first grate carriage and the second gratecarriage have drive arrangements which are independent of one another.It is also possible, however, for the first grate carriage and thesecond grate carriage to have mechanically coupled, opposite directeddrive arrangements. Preferred drive arrangements are hydraulic,pneumatic or electric actuating drives. A cylinder/piston subassembly isparticularly preferred here. The independent drive arrangements allowthe two grate carriages to be controlled individually. It is alsopossible for the first grate carriage to have two drive arrangements andfor the second grate carriage to have one drive arrangement. On the onehand, this makes it possible for the first grate carriage (primarycarriage) to require smaller drive arrangements, which allowstraightforward and quick exchange during operation. On the other hand,by virtue of the drive arrangements being provided laterally andcentrally on the first and the second grate carriages, the forces towhich the grate element is subjected are distributed uniformly.

In a preferred embodiment, the first grate carriage and the second gratecarriage are moved cyclically in counter-phase. This means that, whenthe first grate carriage executes a forward movement, the second gratecarriage executes a rearward movement. In a further preferredembodiment, the first grate carriage and the second grate carriage aremoved cyclically in phase, which means that the first grate carriage andthe second grate carriage are moved simultaneously over differentmovement sections.

It is preferably the case that, within the same row of grate blocks, oneto seven, particularly preferably three to five, grate blocks locateddirectly one beside the other, and together constituting a group ofgrate blocks, have the same movement direction, i.e. they are assignedto the same grate carriage. This achieves an optimum intermixing effect.

In the case of the grate element according to the invention, in eachcase one fixed row of grate blocks is followed in the transportingdirection by a moveable row of grate blocks. However, it is alsopossible for a plurality of moveable rows of grate blocks to followdirectly one after the other. Such an embodiment is preferably selectedwhen very intensive intermixing is necessary.

A grate of a waste-incineration plant preferably has at least one grateelement according to the invention. A further preferred variant is forall the grate elements to be grate elements according to the invention.

The invention will now be explained in more detail with reference to thedrawings. Equivalent parts are provided with the same designations.

In the drawings:

FIG. 1 shows an exemplary embodiment of a first grate carriage;

FIG. 2 shows an exemplary embodiment of a second grate carriage;

FIG. 3 shows the grate carriages shown in FIGS. 1 and 2, together;

FIG. 4 shows the bottom view of the grate carriages shown in FIG. 3;

FIG. 5 shows a first grate carriage with first brackets and firstblock-holding-tube portions;

FIG. 6 shows a second grate carriage with second brackets and secondblock-holding-tube portions;

FIG. 7 shows the grate carriages shown in FIGS. 5 and 6, in an endposition;

FIG. 8 shows the grate carriages shown in FIGS. 5 and 6, in a centralposition;

FIG. 9 shows a grate element with an W formation in the first endposition;

FIG. 10 shows a grate element with an W formation in the second endposition;

FIG. 11 shows a grate element with a X formation in the first endposition;

FIG. 12 shows a grate element with a X formation in the second endposition;

FIG. 13 shows a grate element with conventional grate-block guidance inthe first end position; and

FIG. 14 shows a grate element with conventional grate-block guidance inthe second end position.

FIG. 1 shows a first grate carriage 5. The grate carriage has twoparallel first longitudinal members 9 with a hollow profile and firstcrossmembers 11, which are arranged at right angles thereto and have a Uprofile which is open in the downward direction. The crossbars 11 areintended for bearing brackets with block-holding-tube portions for afirst number of grate blocks of the moveable rows of grate blocks. Thefirst crossmembers 11 are preferably arranged at equal distances fromone another. The first grate carriage 5 is moved forward and back, viarollers 15, on running surfaces 17 of a rail element 19. The endposition of the cylinders 27 constitutes at the same time the rear stopand the front stop, and thus defines the end position of the gratecarriage 5. The first grate carriage is driven by means of acylinder/piston subassembly 25. A piston 29 is located within thecylinder 27. The first longitudinal member 9 is connected, via anarticulation 33, to a piston rod 31 which, in turn, is connected to thepiston 29. Two guide elements, each in the form of a guide groove 23,are located on the two inner walls of the two first longitudinal members9. The guide grooves 23 are intended for interacting with four guidenoses of a second grate carriage. The first grate carriage 5 is intendedfor moving a first number of moveable grate blocks.

FIG. 2 shows the second grate carriage 35 with two parallel secondlongitudinal members 37, with an L profile, running in the transportingdirection. Located between the second longitudinal members 37 are twocrossmembers 39 with a U profile which is open in the downwarddirection, these being intended for bearing brackets with block-holdingtubes for a second number of grate blocks of the moveable rows of grateblocks. The second crossmembers 39 are preferably arranged at equaldistances from one another. The second grate carriage 35, moreover, hastwo guide elements, each in the form of a guide nose 41, on the outersurface of the second longitudinal members 37, these guide elementsbeing intended for interacting with the four guide grooves 23 of thefirst grate carriage 5. The second grate carriage 35 is driven by meansof a second cylinder/piston subassembly 43. The cylinder 27 is coupled,via a piston rod 31, to a third longitudinal member 45, with arectangular hollow profile, which is connected to the secondcrossmembers 39. The crossmembers here have U-shaped recesses 47, inwhich the third longitudinal member 45 is arranged.

FIG. 3 shows the first grate carriage 5 and the second grate carriage35. The four guide grooves 23 of the first grate carriage 5 interactwith the guide noses 41 of the second grate carriage 35. The firstcrossmembers 11 are arranged alternately with the second crossmembers 39of the second grate carriage 35. However, it would also be conceivablefor a plurality of crossmembers of the same grate carriage to followdirectly one after the other. The first cylinder/piston subassembly 25of the first grate carriage 5 [lacuna] is independent of the secondcylinder/piston subassembly 43.

FIG. 4 shows the first grate carriage 5 and the second grate carriage 35from beneath. The two first longitudinal members 9 of the first gratecarriage 5 have, on the undersides, cutouts 49 for the rollers 15. Therail elements 19 serve for supporting the first grate carriage 5 on agrate trough. Moreover, the top side of the wedge-shaped rail element 19serves as a running surface 17 for the rollers 15. The piston rod 31 ofthe first cylinder/piston subassembly 25 is connected to the firstlongitudinal member 9 via an articulation 33 fitted on the underside ofthe longitudinal member 9. The piston rod 31 of the secondcylinder/piston subassembly 43 is connected to the third longitudinalmember 45 of the second grate carriage 35 via an articulation 33. Theguide grooves 23 interact with the guide noses 41 and ensure that thesecond grate carriage 35 moves on a predetermined track.

FIG. 5 shows the first grate carriage 5. First s-shaped brackets 51 arearranged on the first crossmembers 11. The first block-holding-tubeportions 53 are arranged on the first s-shaped brackets 51. These twoportions are intended for bearing a first number of grate blocks of themoveable rows of grate blocks. In this case, three to four grate blocksare assigned in each case to a first block-holding-tube portion 53,these grate blocks together forming a group of grate blocks. The firstblock-holding-tube portions 53 extend only over part of the firstcrossmember 11. It is preferable for three to four first brackets 51 tobe arranged on a first crossmember 11. Stationary brackets 55 with thestationary block-holding-tubes 57 arranged thereon are shownschematically between the first brackets 51 arranged on the firstcrossmembers.

FIG. 6 shows the second grate carriage 35. Second brackets 59 arearranged on the second crossmembers 39. Second block-holding-tubeportions 61 are arranged on the second s-shaped brackets 59. These tubeportions are intended for bearing a second number of grate blocks of themoveable rows of grate blocks. The second brackets 59 are arranged onthe second crossmembers 39 in a mirror-inverted manner in relation tothe first brackets 51 on the first crossmembers 11. The secondblock-holding-tube portions 61 extend only over a part of the secondcrossmember 39. It is preferable for three to four second brackets 59with block-holding-tube portions 61 to be arranged on a secondcrossmember 39. The stationary brackets 55 with the stationaryblock-holding tubes 57 arranged thereon are shown schematically betweenthe second brackets 59 arranged on the second crossmembers 39.

The first and second grate carriages 5, 35 shown in FIGS. 5 and 6 areshown in the assembled state in FIG. 7. The grate carriages 5, 35 are inan end position, i.e. the rollers 15 of the first grate carriage 5 arelocated at the end of the running surface 17. Within a moveable row ofgrate blocks 63, the first brackets 51 with the first block-holding-tubeportions 53 alternate with the second brackets 59 with the secondblock-holding-tube portions 61. The brackets 51, 59′, 51′, 59″ of themoveable grate blocks arranged in a line in the transporting directionare assigned in an alternating manner to the first or the second gratecarriages 5, 35. However, it is also conceivable for the brackets of themoveable grate blocks arranged in a line in the transporting directionto be assigned to one grate carriage.

The embodiment shown in FIG. 7 is shown in a central position in FIG. 8,i.e the rollers 15 of the first grate carriage 5 are located on thecenter of the running surface 17. The axes of all the block-holding-tubeportions 53, 61 of the movable rows 63 of grate blocks and theblock-holding tubes 51 of the fixed rows 65 of grate blocks, in theposition shown, are located in one plane.

FIG. 9 shows an embodiment of the grate element 1 according to theinvention in a W position. In this case, fixed rows 65 of grate blocksare arranged in an alternating manner in relation to moveable rows 63 ofgrate blocks. In each case three or four grate blocks 67, which form agroup 70 of grate blocks, are arranged on the first block-holding-tubeportions 53 of the first grate carriage 5. The groups of grate blocks ofthe same row of grate blocks are assigned in an alternating manner tothe first and the second grate carriages 5, 35. The forward and rearwardmovement of the first grate carriage and of the second grate carriagecauses the group 70 a of grate blocks to be displaced rearward and thegroup 70 b of grate blocks to be displaced forward. As a result, thewaste located on the surface of the group 70 a of grate blocks is pushedaway from the group 70 a of grate blocks by the grate blocks 67 a of thefixed row of grate blocks and is circulated laterally and in thetransporting direction, which gives rise to optimum circulation. Thegroup 70 b of grate blocks, in contrast, is displaced forward and pushesaway the waste on the surface of the fixed row of grate blocks. Thegroups 70 a, 70 b′ of moveable grate blocks arranged in a line in thetransporting direction are assigned in an alternating manner to thefirst grate carriage or the second grate carriage. If the groups 70 a,70 b′ of grate blocks are pushed forward, a very steep gradient isproduced by way of the fixed row of grate blocks located therebetween,whereas the same groups of grate blocks have a shallow gradient if theyare displaced rearward. The garbage is thus intermixed more or lessrandomly. In the end position, a so-called W position is formed sincethe rear groups 70 b, 70 a′, 70 b″, 70 a″, 70 b′″ of grate blocks of twomoveable rows of grate blocks are in the shape of the letter W 80. Suchan arrangement results in the waste which is to be incinerated beingoptimally intermixed, raked and conveyed.

That embodiment of the grate elements according to the invention whichis shown in FIG. 9 is shown in the other end position in FIG. 10. Inthis case, those groups of grate blocks which are shown at the rear inFIG. 9 are now at the front, while those which are shown at the frontare now arranged at the rear.

FIG. 11 shows a further embodiment of the grate according to theinvention in an X position. In this case, fixed rows 65 of grate blocksare arranged in an alternating manner in relation to moveable rows 63 ofgrate blocks. In each case three or four grate blocks 67, which form agroup 70 of grate blocks, are arranged on the first block-holding-tubeportions 53 of the first grate carriage 5. The groups 70 a, 70 a′ ofgrate blocks of the same row of grate blocks are assigned in analternating manner to the first grate carriage and the second gratecarriage. The grate blocks of the moveable grate blocks arranged in aline in the transporting direction are assigned in each case to thefirst grate carriage or the second grate carriage. As a result, in theend position, an X position is formed since the front groups 70 a, 70a′″ and 70 a′, 70 a″ of grate blocks of two moveable rows of grateblocks are in the shape of the letter X 82.

That embodiment of the grate element 1 according to the invention whichis shown in FIG. 11 is shown in the other end position in FIG. 12. Inthis case, those groups of grate blocks which are shown at the rear inFIG. 11 are now at the front, while those which are shown at the frontare now arranged at the rear.

FIG. 13 shows a further embodiment of the grate element 1 according tothe invention, allowing operation as has been known up until now. Inthis case, fixed rows 65 of grate blocks are arranged in an alternatingmanner in relation to moveable rows 63 of grate blocks. In each casethree or four grate blocks 67, which form a group 70 of grate blocks,are arranged on the first block-holding-tube portions 53 of the firstgrate carriage 5. The groups of grate blocks of the same row of grateblocks are assigned in an alternating manner to the first grate carriageand the second grate carriage. The first grate carriage and the secondgrate carriage move such that the grate blocks of the two gratecarriages move in the same direction at the same point in time. Thisshows the extraordinary flexibility of the grate element 1 according tothe invention, since allowance can be made, as desired, for therespective ambient conditions in each operating phase by correspondingactivation of the cylinder/piston subassemblies.

That embodiment of the grate element according to the invention which isshown in FIG. 13 is shown in the other end position in FIG. 14.

1. A grate element for a grate of a waste-incineration plant, having aplurality of fixed or moveable rows of grate blocks arranged one behindthe other, in each case one fixed row of grate blocks being followed byat least one moveable row of grate blocks, and a plurality of grateblocks being arranged in each row of grate blocks, wherein a firstnumber of grate blocks arranged in a moveable row of grate blocks isassigned to a first grate carriage, and a second number of grate blocksarranged in the moveable row of grate blocks is assigned to a secondgrate carriage, it being possible for the first number of grate blocksto be moved independently of the second number of grate blocks, whereinthe first grate carriage and the second grate carriage are movedcyclically in phase.
 2. A grate element for a grate of awaste-incineration plant, having a plurality of fixed or moveable rowsof grate blocks arranged one behind the other, in each case one fixedrow of grate blocks being followed by at least one moveable row of grateblocks, and a plurality of grate blocks being arranged in each row ofgrate blocks, wherein a first number of grate blocks arranged in amoveable row of grate blocks is assigned to a first grate carriage, anda second number of grate blocks arranged in the moveable row of grateblocks is assigned to a second grate carriage, it being possible for thefirst number of grate blocks to be moved independently of the secondnumber of grate blocks, wherein the moveable grate blocks arranged in aline in the transporting direction are assigned to the same gratecarriage.
 3. A grate carriage for a grate element for a grate of awaste-incineration plant, the grate element having a plurality of fixedor moveable rows of grate blocks arranged one behind the other, in eachcase one fixed row of grate blocks being followed by at least onemoveable row of grate blocks, and a plurality of grate blocks beingarranged in each row of grate blocks, wherein a first number of grateblocks arranged in a moveable row of grate blocks is assigned to a firstgrate carriage, and a second number of grate blocks arranged in themoveable row of grate blocks is assigned to a second grate carriage, itbeing possible for the first number of grate blocks to be movedindependently of the second number of grate blocks, and the gratecarriage having crossmembers which are intended for bearing a pluralityof block-holding-tube portions for a moveable row of grate blocks, theblock-holding-tube portions of the moveable grate blocks extending onlyover part of the grate-carriage width.